Methods for fabricating polycrystalline diamond compacts using at least one preformed transition layer and resultant polycrystalline diamond compacts

ABSTRACT

Embodiments relate to polycrystalline diamond compacts (“PDCs”) that are less susceptible to liquid metal embrittlement damage due to the use of at least one transition layer between a polycrystalline diamond (“PCD”) layer and a substrate. In an embodiment, a PDC includes a PCD layer, a cemented carbide substrate, and at least one transition layer bonded to the substrate and the PCD layer. The at least one transition layer is formulated with a coefficient of thermal expansion (“CTE”) that is less than a CTE of the substrate and greater than a CTE of the PCD layer. At least a portion of the PCD layer includes diamond grains defining interstitial regions and a metal-solvent catalyst occupying at least a portion of the interstitial regions. The diamond grains and the catalyst collectively exhibit a coercivity of about 115 Oersteds or more and a specific magnetic saturation of about 15 Gauss·cm 3 /grams or less.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.13/087,775 filed on 15 Apr. 2011, the disclosure of which isincorporated herein, in its entirety, by this reference.

BACKGROUND

Wear-resistant, polycrystalline diamond compacts (“PDCs”) are utilizedin a variety of mechanical applications. For example, PDCs are used indrilling tools (e.g., cutting elements, gage trimmers, etc.), machiningequipment, bearing apparatuses, wire-drawing machinery, and in othermechanical apparatuses.

PDCs have found particular utility as superabrasive cutting elements inrotary drill bits, such as roller-cone drill bits and fixed-cutter drillbits. A PDC cutting element typically includes a superabrasive diamondlayer commonly known as a diamond table. The diamond table is formed andbonded to a substrate using a high-pressure/high-temperature (“HPHT”)process. The PDC cutting element may also be brazed directly into apreformed pocket, socket, or other receptacle formed in a bit body. Thesubstrate may often be brazed or otherwise joined to an attachmentmember, such as a cylindrical backing A rotary drill bit typicallyincludes a number of PDC cutting elements affixed to the bit body. It isalso known that a stud carrying the PDC may be used as a PDC cuttingelement when mounted to a bit body of a rotary drill bit bypress-fitting, brazing, or otherwise securing the stud into a receptacleformed in the bit body.

Conventional PDCs are normally fabricated by placing a cemented carbidesubstrate into a container or cartridge with a volume of diamondparticles positioned on a surface of the cemented carbide substrate. Anumber of such cartridges may be loaded into an HPHT press. Thesubstrate(s) and volume of diamond particles are then processed underHPHT conditions in the presence of a catalyst material that causes thediamond particles to bond to one another to form a matrix of bondeddiamond grains defining a polycrystalline diamond (“PCD”) table. Thecatalyst material is often a metal-solvent catalyst (e.g., cobalt,nickel, iron, or alloys thereof) that is used for promoting intergrowthof the diamond particles.

In one conventional approach, a constituent of the cemented carbidesubstrate, such as cobalt from a cobalt-cemented tungsten carbidesubstrate, liquefies and sweeps from a region adjacent to the volume ofdiamond particles into interstitial regions between the diamondparticles during the HPHT process. The cobalt acts as a metal-solventcatalyst to promote intergrowth between the diamond particles, whichresults in the formation of a matrix of bonded diamond grains havingdiamond-to-diamond bonding therebetween, with interstitial regionsbetween the bonded diamond grains being occupied by the metal-solventcatalyst.

Despite the availability of a number of different types of PDCs,manufacturers and users of PDCs continue to seek PDCs with improved wearresistance, thermal stability, and manufacturability.

SUMMARY

Embodiments of the invention relate to a PDC that is less susceptible tobrazing damage due to the use of at least one transition layer disposedbetween at least one PCD layer and a substrate thereof. It is currentlybelieved that including the at least one transition layer between thePCD layer and the substrate may reduce the tensile stresses present inthe substrate to make the substrate less susceptible to liquid metalembrittlement (“LME”) and help reduce the tensile stresses generated inthe PCD layer during brazing of the PDC to another structure such as adrill bit body to help prevent damage to the PCD layer during brazing.Methods for manufacturing a PDC that includes at least one transitionlayer between the PCD table and the substrate and embodiments utilizingthe disclosed PDCs in various articles and apparatuses, such as rotarydrill bits, bearing apparatuses, wire-drawing dies, machining equipment,and other articles and apparatuses are also disclosed.

In an embodiment, a PDC includes at least one PCD layer, a cementedcarbide substrate, and at least one transition layer disposed betweenand bonded to the cemented carbide substrate and the PCD layer. The atleast one transition layer is formulated with a coefficient of thermalexpansion (“CTE”) that is less than a CTE of the cemented carbidesubstrate and greater than a CTE of the at least one PCD layer. At leasta portion of the at least one PCD layer includes a plurality of diamondgrains defining a plurality of interstitial regions and a metal-solventcatalyst occupying at least a portion of the plurality of interstitialregions. The plurality of diamond grains and the metal-solvent catalystcollectively may exhibit a coercivity of about 115 Oersteds (“Oe”) ormore and a specific magnetic saturation of about 15 Gauss·cm³/grams(“G·cm³/g”) or less.

In another embodiment, a method for manufacturing a PDC is described.The method includes disposing at least one layer that includes aplurality of diamond grains and at least one additive between at leastone layer of diamond particles and a cemented carbide substrate in apressure transmitting medium to form a cell assembly, and subjecting thecell assembly to an HPHT process of a temperature of at least 1000° C.and a pressure of at least 7.5 GPa in the pressure transmitting mediumto form a PDC. The PDC so-formed includes at least one PCD layer, acemented carbide substrate, and at least one transition layer disposedbetween the PCD layer and the cemented carbide substrate. The at leastone transition layer exhibits a CTE that is less than a CTE of thecemented carbide substrate and greater than a CTE of the PCD layer.

Further embodiments relate to applications utilizing the disclosed PCDand PDCs in various articles and apparatuses, such as rotary drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses.

Features from any of the disclosed embodiments may be used incombination with one another, without limitation. In addition, otherfeatures and advantages of the present disclosure will become apparentto those of ordinary skill in the art through consideration of thefollowing detailed description and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate several embodiments of the invention, whereinidentical reference numerals refer to identical or similar elements orfeatures in different views or embodiments shown in the drawings.

FIG. 1A is a cross-sectional view of a PDC that includes at least onePCD layer, a substrate, and at least one transition layer disposedbetween and bonded to the substrate and the PCD layer according to anembodiment.

FIG. 1B is a cross-sectional view of the PDC shown in FIG. 1A afterleaching the PCD layer according to an embodiment.

FIG. 2 is a schematic diagram illustrating a method for fabricating thePDC shown in FIG. 1A according to an embodiment.

FIG. 3 is a side cross-sectional view of an assembly for forming a PDCaccording to another embodiment.

FIG. 4 is a side cross-sectional view of the PDC formed by HPHTsintering the assembly shown in FIG. 3.

FIG. 5 illustrates finite element modeling results showing reducedbraze-temperature tensile stresses in the PCD layer of the PDC shown inFIG. 1A when the tungsten carbide content is varied in the translationlayer according to various embodiments.

FIG. 6 illustrates a method for fabricating a PDC that includes highpressure annealing according to an embodiment.

FIG. 7 illustrates a comparison between the residual stress in anun-annealed PDC and a PDC annealed using a low pressure annealingprocess.

FIG. 8A is an isometric view of an embodiment of a rotary drill bit thatmay employ one or more of the disclosed PDC embodiments.

FIG. 8B is a top elevation view of the rotary drill bit shown in FIG.8A.

FIG. 9 is an isometric cut-away view of an embodiment of athrust-bearing apparatus that may utilize one or more of the disclosedPDC embodiments.

FIG. 10 is an isometric cut-away view of an embodiment of a radialbearing apparatus that may utilize one or more of the disclosed PDCembodiments.

DETAILED DESCRIPTION

Embodiments of the invention relate to a PDC that is less susceptible tobrazing damage due to the use of at least one transition layer disposedbetween at least one PCD layer and a substrate (e.g., a cemented carbidesubstrate) thereof. It is currently believed that including the at leastone transition layer between the PCD layer and the substrate can reducethe stresses present in the substrate to make the substrate lesssusceptible to LME and help reduce the stresses generated in the PCDlayer (e.g., during brazing of the PDC to another structure such as adrill bit body) to help prevent damage of the PCD layer. Methods formanufacturing a PDC that includes at least one transition layer betweenthe PCD layer and the substrate and embodiments utilizing the disclosedPDCs in various articles and apparatuses, such as rotary drill bits,bearing apparatuses, wire-drawing dies, machining equipment, and otherarticles and apparatuses are also disclosed.

Referring to FIG. 1A, an embodiment of a PDC 100 includes at least onePCD layer 106, a substrate 102, and at least one transition layer 104disposed between and bonded to the substrate 102 and the PCD layer 106.The PCD layer 106 exhibits at least one working surface 114 having atleast one lateral dimension “d” (e.g., a diameter), at least one lateralsurface 115, and an optional chamfer 117 extending between the workingsurface 114 and the at least one lateral surface 115. Although FIG. 1Ashows the working surface 114 as substantially planar, the workingsurface 114 may be concave, convex, or another non-planar geometry. Thesubstrate 102 may be generally cylindrical or another selectedconfiguration, without limitation. The substrate 102 may include,without limitation, cemented carbides, such as tungsten carbide,titanium carbide, chromium carbide, niobium carbide, tantalum carbide,vanadium carbide, or combinations thereof cemented with iron, nickel,cobalt, or alloys thereof. For example, in an embodiment, the substrate102 comprises cobalt-cemented tungsten carbide.

The PCD layer 106 includes a plurality of diamond grains directly bondedtogether via diamond-to-diamond bonding (e.g., sp³ bonding) to define aplurality of interstitial regions. At least a portion of theinterstitial regions or, in some embodiments, substantially all of theinterstitial regions may be occupied by a metal-solvent catalyst, suchas iron, nickel, cobalt, or alloys of any of the foregoing metals. ThePCD layer 106 may exhibit an average grain size of about 50 μm or less,such as about 30 μm or less or about 20 μm or less. For example, theaverage grain size of the diamond grains may be about 10 μm to about 18μm and, in some embodiments, about 15 μm to about 25 μm. In someembodiments, the average grain size of the diamond grains may be about10 μm or less, such as about 2 μm to about 5 μm or submicron.

According to various embodiments, when the PCD layer 106 is sintered ata pressure of at least about 7.5 GPa, the PCD layer 106 may exhibit acoercivity of 115 Oe or more, a high-degree of diamond-to-diamondbonding, a specific magnetic saturation about 15 G·cm³/g or less, and ametal-solvent catalyst content of about 7.5 weight % (“wt %”) or less.For example, the PCD layer 106 may exhibit a coercivity of 115 Oe ormore, a high-degree of diamond-to-diamond bonding, a specific magneticsaturation about 15 G·cm³/g or less, and a metal-solvent catalystcontent of about 7.5 wt % or less, such as about 1 wt % to about 7.5 wt%, about 1 wt % to about 6 wt %, about 3 wt % to about 6 wt %, less thanabout 3 wt %, or a residual amount to about 1 wt %.

As discussed above, the metal-solvent catalyst that occupies at least aportion of the interstitial regions of the PCD layer 106 may be presentin the PCD layer 106 in an amount of about 7.5 wt % or less, such asabout 1 wt % to about 7.5 wt %, about 1 wt % to about 6 wt %, about 3 wt% to about 6 wt %, less than about 3 wt %, or a residual amount to about1 wt %. By maintaining the metal-solvent catalyst content below about7.5 wt %, the PCD layer 106 may exhibit a desirable level of thermalstability suitable for subterranean drilling applications.

As will be discussed in more detail in connection with FIG. 5 below, thetransition layer 104 may help to reduce and/or moderate the residualtensile stresses in the substrate 102 generated during fabrication ofthe PDC 100 and may also help to reduce the thermal-induced tensilestresses generated in the PCD layer 106 during brazing of the PDC 100 toanother structure such as a drill bit body. This is because the CTE ofthe transition layer 104 is specifically chosen to be less than that ofthe underlying substrate 102 and greater than that of the PCD layer 106.For example, the CTE of the transition layer 104 may be about 1.02 toabout 5 times (e.g., about 1.2 to about 3, about 2 to about 3, or about2.5 to about 3.5) greater than that of the PCD layer 106. For example,when the transition layer 104 includes about 2 vol % of tungsten carbidewith the balance being substantially diamond grains and cobalt, the CTEmay be 1.02 times greater than the CTE of the PCD layer 106. As anotherexample, when the transition layer 104 includes about 10 vol % oftungsten carbide with the balance being substantially diamond grains andcobalt, the CTE may be 1.1 times greater than the CTE of the PCD layer106. As yet a further example, when the transition layer 104 includesabout 20 vol % of tungsten carbide with the balance being substantiallydiamond grains and cobalt, the CTE may be 1.2 times greater than the CTEof the PCD layer 106. As the tensile stresses in the substrate 102 arereduced at least proximate to the interfacial surface 108 thereof, LMEmay be reduced and/or eliminated when the substrate 102 is brazed toanother structure using a zinc-containing braze alloy that ordinarilycan potentially cause LME. As the thermal-induced tensile stressesgenerated in the PCD layer 106 during brazing of the PDC 100 arereduced, damage to the PDC table 106 may also be reduced.

The transition layer 104 includes diamond grains and at least oneadditive that together define interstitial regions having themetal-solvent catalyst disposed in at least a portion of theinterstitial regions. The at least one additive may be chosen fromtungsten carbide particles, cemented tungsten carbide particles (e.g.,individual particles formed of tungsten carbide particles cementedtogether with cobalt or a cobalt alloy), chromium carbide particles,cubic boron nitride crystals, or mixtures thereof. For example, thecemented tungsten carbide particles may be formed in by sintering,crushing the sintered product into a plurality of particles, andclassified the crushed particles to a specific particle size range. Theamount of the at least one additive present in the transition layer 104may be about 1 volume % (“vol %”) to about 80 vol % of the transitionlayer 104, such as about 1 vol % to about 50 vol %, about 1 vol % toabout 5 vol %, about 2 vol % to about 5 vol %, about 1 vol % to about 10vol %, about 3 vol % to about 10 vol %, about 2 vol % to about 10 vol %,about 10 vol % to about 25 vol %, about 25 vol % to about 50 vol %, orabout 10 vol % to about 25 vol %, with the balance substantially beingdiamond grains and metal-solvent catalyst. In some embodiments, thetransition layer 104 may include about 10 vol % to about 80 vol %diamond grains (e.g., about 50 vol % to about 75 vol %) and about 1 wt %to about 7 wt % metal-solvent catalyst occupying the interstitialregions between the at least one additive and the diamond grains, andthe balance substantially being the at least one additive (e.g., about18 vol % to about 49 vol %). Depending upon the volume % of the at leastone additive in the transition layer 104, the transition layer 104so-formed may also exhibit diamond-to-diamond bonding between thediamond grains thereof when the volume % of the at least one additive isrelatively low and may exhibit limited or substantially nodiamond-to-diamond bonding when the volume % of the at least oneadditive is relatively high. In some embodiments, the PCD layer 106 maybe substantially free of the at least one additive, while in otherembodiments, a small amount of the at least one additive may migrateinto the PCD layer 106 during formation thereof.

Many physical characteristics of the PCD layer 106 may be determined bymeasuring certain magnetic properties of the PCD layer 106 because themetal-solvent catalyst may be ferromagnetic. The amount of themetal-solvent catalyst present in the PCD layer 106 may be correlatedwith the measured specific magnetic saturation of the PCD layer 106. Arelatively larger specific magnetic saturation indicates relatively moremetal-solvent catalyst in the PCD layer 106.

The mean free path between neighboring diamond grains of the PCD layer106 may be correlated with the measured coercivity of the PCD layer 106.A relatively large coercivity indicates a relatively smaller mean freepath. The mean free path is representative of the average distancebetween neighboring diamond grains of the PCD layer 106 and, thus, maybe indicative of the extent of diamond-to-diamond bonding between thediamond grains in the PCD layer 106. A relatively smaller mean freepath, in well-sintered PCD, may indicate relatively morediamond-to-diamond bonding.

As merely one example, ASTM B886-03 (2008) provides a suitable standardfor measuring the specific magnetic saturation and ASTM B887-03 (2008)e1 provides a suitable standard for measuring the coercivity of the PCDlayer 106. Although both ASTM B886-03 (2008) and ASTM B887-03 (2008) e1are directed to standards for measuring magnetic properties of cementedcarbide materials, either standard may be used to determine the magneticproperties of PCD. A KOERZIMAT CS 1.096 instrument (commerciallyavailable from Foerster Instruments of Pittsburgh, Pa.) is one suitableinstrument that may be used to measure the specific magnetic saturationand the coercivity of the PCD layer 106. To measure the magneticproperties of the PCD layer 106, the PCD layer 106 may be separated fromthe transition layer 104 and the substrate 102 by cutting along theinterface between the PCD layer 106 and the transition layer 104 usingelectrical-discharge machining (e.g., wire electrical-dischargemachining) and/or a grinding process.

Generally, as the sintering pressure that is used to form the PCD layer106 increases, the coercivity of the PCD layer 106 may increase and themagnetic saturation may decrease. The PCD layer 106 defined collectivelyby the bonded diamond grains and the metal-solvent catalyst therein mayexhibit a coercivity of about 115 Oe or more and a metal-solventcatalyst content of less than about 7.5 wt % as indicated by a specificmagnetic saturation of about 15 G·cm³/g or less. In a more detailedembodiment, the coercivity of the PCD layer 106 may be about 115 Oe toabout 250 Oe and the specific magnetic saturation of the PCD layer 106may be greater than zero G·cm³/g to about 15 G·cm³/g. In an even moredetailed embodiment, the coercivity of the PCD layer 106 may be about115 Oe to about 175 Oe and the specific magnetic saturation of the PCDlayer 106 may be about 5 G·cm³/g to about 15 G·cm³/g. In yet an evenmore detailed embodiment, the coercivity of the PCD layer 106 may beabout 155 Oe to about 175 Oe and the specific magnetic saturation of thePCD layer 106 may be about 10 G·cm³/g to about 15 G·cm³/g. The specificpermeability (i.e., the ratio of specific magnetic saturation tocoercivity) of the PCD layer 106 may be about 0.10 G·cm³/Oe·g or less,such as about 0.060 G·cm³/Oe·g to about 0.090 G·cm³/Oe·g. Despite theaverage grain size of the bonded diamond grains being less than about 50μm, the metal-solvent catalyst content in the PCD layer 106 may still beless than about 7.5 wt % resulting in a desirable thermal stability.

A PCD layer formed by sintering diamond grains having the same diamondparticle size distribution as a PCD embodiment of the invention, butsintered at a pressure of, for example, up to about 5.5 GPa and attemperatures in which diamond is stable may exhibit a coercivity ofabout 100 Oe or less and/or a specific magnetic saturation of about 16G·cm³/g or more. Thus, in one or more embodiments of the invention, thePCD layer 106 exhibits a metal-solvent catalyst content of less than 7.5wt % and a greater amount of diamond-to-diamond bonding between diamondgrains than that of a PCD layer sintered at a lower pressure, but withthe same precursor diamond particle size distribution and catalyst.

Referring to FIG. 1B, in some embodiments, at least the PCD layer 106shown in FIG. 1A may be leached to deplete a portion of themetal-solvent catalyst therefrom. The metal-solvent catalyst may be atleast partially removed in a leaching process to form a leached region106′ that extends inwardly from the working surface 114, the chamfer117, and the at least one lateral surface 115. The unaffected underlyingportion of the PCD layer 106 is labeled 106″ in FIG. 1B. For example,the leaching may be performed by exposing at least the PCD layer 106 toan acid (e.g., hydrochloric acid, hydrofluoric acid, nitric acid, ormixtures of the foregoing acids) and/or a gas (e.g., carbon monoxide)for a sufficient time. For example, a leach depth for the leached region106′ may be about 50 μm to about 700 μm, about 250 μm to about 400 μm,about 250 μm to about 350 μm, about 250 μm to about 300 μm, about 250 μmto about 275 μm, or about 500 μm to about 1000 μm. Depending on theleach depth and whether the underlying transition layer 104 is exposedto the leaching acid, in some embodiments, the leached region 106′ mayalso extend into the transition layer 104. After leaching, themetal-solvent catalyst may be present in the leached region 106′ of thePCD layer 106 in amount of about 2 wt % or less, about 0.8 wt % to about1.50 wt %, or about 0.86 wt % to about 1.47 wt %. To measure themagnetic properties of the unaffected underlying portion 106″ of the PCDlayer 106, the leached region 106′ should be removed along with thetransition layer 104 and the substrate 102.

FIG. 2 is a schematic illustration of an embodiment of a method forfabricating the PDC 100 shown in FIG. 1A. Referring to FIG. 2, atransition-layer mixture 110 is positioned adjacent to the interfacialsurface 108 of the substrate 102 and at least one layer of diamondparticles 112 is positioned adjacent to the transition-layer mixture110. Although FIG. 2 shows the interfacial surface 108 of the substrate102 as being substantially planar, the interfacial surface 108 mayexhibit a selected non-planar topography, such as a grooved, ridged, orother non-planar interfacial surface.

The at least one layer of diamond particles 112 may exhibit an averageparticle size of about 50 μm or less, such as about 30 μm or less orabout 20 μm or less. For example, the average particle size of thediamond particles may be about 10 μm to about 18 μm and, in someembodiments, about 15 μm to about 18 μm. In some embodiments, theaverage particle size of the diamond grains may be about 10 μm or less,such as about 2 μm to about 5 μm or submicron. The diamond particlessize distribution of the diamond particles may exhibit a single mode, ormay be a bimodal or greater grain size distribution. Thetransition-layer mixture 110 includes an intermixed blend of a pluralityof diamond particles and at least one additive. Suitable examples forthe at least one additive include, but are not limited to, tungstencarbide, chromium carbide, cubic boron nitride, combinations thereof, orthe like. The amount of the at least one additive present in thetransition-layer mixture 110 may be about 1 vol % to about 80 vol % ofthe transition layer 104, such as about 1 vol % to about 50 vol %, about1 vol % to about 5 vol %, about 2 vol % to about 5 vol %, about 1 vol %to about 10 vol %, about 3 vol % to about 10 vol %, about 2 vol % toabout 10 vol %, about 10 vol % to about 25 vol %, about 25 vol % toabout 50 vol %, or about 10 vol % to about 25 vol %, with the balancesubstantially being diamond particles.

The substrate 102 may include a metal-solvent catalyst (e.g., cobalt)therein. The at least one layer of diamond particles 112, thetransition-layer mixture 110, and the substrate 102 may be subjected toan HPHT process using HPHT conditions previously described. The PDC 100so-formed includes the PCD layer 106 integrally formed with thetransition layer 104 and the substrate 102. The transition layer 104 isbonded to the interfacial surface 108 of the substrate 102 and, in turn,the PCD layer 106 is bonded to the transition layer 104.

The substrate 102, the transition-layer mixture 110, and at least onelayer of diamond particles 112 may be arranged in a pressuretransmitting medium to form a cell assembly. The cell assembly with thepressure transmitting medium enclosing the substrate 102, thetransition-layer mixture 110, and the at least one layer of diamondparticles 112 disposed therein may be subjected to an HPHT process usingan ultra-high pressure press at a temperature of at least about 1000° C.(e.g., about 1100° C. to about 2200° C., or about 1200° C. to about1450° C.) and a pressure in the pressure transmitting medium of at leastabout 7.5 GPa (e.g., about 7.5 GPa to about 15 GPa) for a timesufficient to sinter the diamond particles together in the presence ofthe metal-solvent catalyst to form the PCD layer 106 and the transitionlayer 104 from the transition-layer mixture 110 that bonds the PCD layer106 to the substrate 102.

In order to efficiently sinter the diamond particles of the at least onelayer of diamond particles 112 and the transition-layer mixture 110, thesubstrate 102, the transition-layer mixture 110, and the at least onelayer of diamond particles 112 may be enclosed in a pressuretransmitting medium, such as a refractory metal can, graphite structure,pyrophyllite, or other suitable pressure transmitting structure to formthe cell assembly. Examples of suitable gasket materials and cellstructures for use in manufacturing PDCs are disclosed in U.S. Pat. No.6,338,754 and U.S. patent application Ser. No. 11/545,929, each of whichis incorporated herein, in its entirety, by this reference. Anotherexample of a suitable pressure transmitting material is pyrophyllite,which is commercially available from Wonderstone Ltd. of South Africa.The cell assembly, including the contents therein, may subjected to anHPHT process using an ultra-high pressure press at a temperature of atleast about 1000° C. (e.g., about 1100° C. to about 2200° C., or about1200° C. to about 1450° C.) and a pressure in the pressure transmittingmedium of at least about 7.5 GPa (e.g., about 7.5 GPa to about 15 GPa)for a time sufficient to sinter the diamond particles of the at leastone layer of diamond particles 112 together in the presence of themetal-solvent catalyst to form the PCD layer 106 and sinter thetransition-layer mixture 110 together to form the transition layer 104that bonds the PCD layer 106 to the substrate 102. The PCD layer 106 soformed includes a matrix of PCD comprising bonded diamond grainsdefining interstitial regions occupied by the metal-solvent catalyst.For example, the pressure in the pressure transmitting medium employedin the HPHT process may be at least about 8.0 GPa, at least about 9.0GPa, at least about 10.0 GPa, at least about 11.0 GPa, at least about12.0 GPa, or at least about 14 GPa.

The pressure values employed in the HPHT processes disclosed hereinrefer to the pressure in the pressure transmitting medium at roomtemperature (e.g., about 25° C.) with application of pressure using anultra-high pressure press and not the pressure applied to the exteriorof the cell assembly. The actual pressure in the pressure transmittingmedium at sintering temperature may be slightly higher. The ultra-highpressure press may be calibrated at room temperature by embedding atleast one calibration material that changes structure at a knownpressure such as, PbTe, thallium, barium, or bismuth in the pressuretransmitting medium. Further, optionally, a change in resistance may bemeasured across the at least one calibration material due to a phasechange thereof. For example, PbTe exhibits a phase change at roomtemperature at about 6.0 GPa and bismuth exhibits a phase change at roomtemperature at about 7.7 GPa. Examples of suitable pressure calibrationtechniques are disclosed in G. Rousse, S. Klotz, A. M. Saitta, J.Rodriguez-Carvajal, M. I. McMahon, B. Couzinet, and M. Mezouar,“Structure of the Intermediate Phase of PbTe at High Pressure,” PhysicalReview B: Condensed Matter and Materials Physics, 71, 224116 (2005) andD. L. Decker, W. A. Bassett, L. Merrill, H. T. Hall, and J. D. Barnett,“High-Pressure Calibration: A Critical Review,” J. Phys. Chem. Ref.Data, 1, 3 (1972).

In an embodiment, a pressure of at least about 7.5 GPa in the pressuretransmitting medium may be generated by applying pressure to a cubichigh-pressure cell assembly that encloses the substrate 102, thetransition-layer mixture 110, and the at least one layer of diamondparticles 112 using anvils, with each anvil applying pressure to adifferent face of the cubic high-pressure assembly. In such anembodiment, a surface area of each anvil face of the anvils may beselectively dimensioned to facilitate application of pressure of atleast about 7.5 GPa to the cell assembly. For example, the surface areaof each anvil may be less than about 12.0 cm², such as about 8 cm² toabout 10 cm². The anvils may be made from a cobalt-cemented tungstencarbide or other material having a sufficient compressive strength tohelp reduce damage thereto through repetitive use in a high-volumecommercial manufacturing environment. Optionally, as an alternative toor in addition to selectively dimensioning the surface area of eachanvil face, two or more internal anvils may be embedded in the cubichigh-pressure cell assembly to further intensify pressure. For example,the article W. Utsumi, N. Toyama, S. Endo and F. E. Fujita, “X-raydiffraction under ultra-high pressure generated with sintered diamondanvils,” J. Appl. Phys., 60, 2201 (1986) is incorporated herein, in itsentirety, by this reference and discloses that sintered diamond anvilsmay be embedded in a cubic pressure transmitting medium for intensifyingthe pressure applied by an ultra-high pressure press to a workpiece alsoembedded in the cubic pressure transmitting medium.

If the substrate 102 includes a metal-solvent catalyst (e.g., cobalt ina cobalt-cemented tungsten carbide substrate), the metal-solventcatalyst therein may liquefy and infiltrate the transition-layer mixture110 and the at least one layer of diamond particles 112 to promotegrowth between adjacent diamond particles of the at least one layer ofdiamond particles 112 and the transition-layer mixture 110 to form thePCD layer 106 and the transition layer 104. For example, if thesubstrate 102 is a cobalt-cemented tungsten carbide substrate, cobaltfrom the substrate 102 may be liquefied and infiltrate the at least onelayer of diamond particles 112 and the transition-layer mixture 110 tocatalyze formation of diamond-to-diamond bonding in at least the PCDlayer 106. Depending upon the volume % of the at least one additive inthe transition-layer mixture 110, the transition layer 104 so-formed mayalso exhibit diamond-to-diamond bonding between the diamond grainsthereof when the volume % of the at least one additive is relatively lowand may exhibit limited or substantially no diamond-to-diamond bondingwhen the volume % of the at least one additive is relatively high.

Employing selectively dimensioned anvil faces and/or internal anvils inthe ultra-high pressure press used to process the at least one layer ofdiamond particles 112 and the transition-layer mixture 110 and substrate102 enables forming the at least one lateral dimension “d” of the PCDlayer 106 to be about 0.80 cm or more. Referring again to FIG. 1A, forexample, at least one lateral dimension “d” may be about 0.80 cm toabout 3.0 cm and, in some embodiments, about 1.3 cm to about 1.9 cm orabout 1.6 cm to about 1.9 cm. A representative volume of the PCD layer106 formed using the selectively dimensioned anvil faces and/or internalanvils may be at least about 0.050 cm³. For example, the volume may beabout 0.25 cm³ to at least about 1.25 cm³ or about 0.1 cm³ to at leastabout 0.70 cm³. A representative volume for the PDC 100 may be about 0.4cm³ to at least about 4.6 cm³, such as about 1.1 cm³ to at least about2.3 cm³.

In other embodiments, a PCD layer according to an embodiment may beseparately formed using a HPHT sintering process and, subsequently,bonded to the transition layer 104 by brazing, using a separate HPHTbonding process, or any other suitable joining technique, withoutlimitation. For example, the PCD layer so-formed may be leached toremove substantially all of the metal-solvent catalyst therefrom andbonded to the transition layer 104 during or after formation of thetransition layer 104. In an embodiment, the leached PCD layer may bebonded to the transition layer 104 in an HPHT process during or afterformation of the transition layer 104, and a metallic infiltrant (e.g.,cobalt from a cobalt-cemented tungsten carbide substrate) may infiltrateinto the leached PCD layer during the HPHT process. In a furtherembodiment, the metallic infiltrant may be leached from the infiltratedPCD layer to a selected depth from an exterior working surface thereof.In yet another embodiment, a substrate may be formed by depositing abinderless carbide (e.g., tungsten carbide via chemical vapordeposition) onto the separately formed PCD layer and transition layer.

In some embodiments, at least the PCD layer 106 shown in FIG. 2 may beleached to deplete a portion of the metal-solvent catalyst therein andform the leached region 106′ shown in FIG. 1B. For example, the leachingmay be performed by exposing at least the PCD layer 106 to an acid(e.g., hydrochloric acid, hydrofluoric acid, nitric acid, or mixtures ofthe foregoing acids) and/or a gas (e.g., carbon monoxide) for asufficient time. Depending on the leach depth and whether the underlyingtransition layer 104 is exposed to the leaching acid, in someembodiments, the leached region 106′ may also extend into the transitionlayer 104.

Although the PDC 100 illustrated in FIG. 1A includes only one transitionlayer 104, in other embodiments, a PDC may include more than two or moretransition layers. Referring to FIG. 3, an assembly 130 includes thesubstrate 102, at least one layer of diamond particles 112, a firsttransition-layer mixture 132 adjacent to the layer of diamond particles112, and a second transition-layer mixture 134 adjacent to the substrate102. In an embodiment, the first transition-layer mixture 132 mayinclude less of the at least one additive and more diamond particlesthan that of the second transition-layer mixture 134 adjacent to thesubstrate 102. In an embodiment, when the substrate 102 is fabricatedfrom cemented tungsten carbide, the at least one additive in the firsttransition-layer mixture 132 may include a mixture of tungsten-carbideparticles, cemented tungsten carbide particles, or the like in an amountof about 25 vol % and diamond particles in an amount of about 75 vol %,and the second transition-layer mixture 134 may include a mixture oftungsten-carbide particles in an amount of about 50 vol % and diamondparticles in an amount of about 50 vol %. A metal-solvent catalyst, suchas cobalt, nickel, iron, or an Invar®-type iron-nickel alloy, may alsobe intentionally mixed to the first and second transition-layer mixtures132 and 134 in particulate form.

Referring to FIG. 4, after HPHT processing of the assembly 130 using anyof the HPHT conditions disclosed herein, a PDC 136 is formed. The PDC136 includes at least one PCD layer 138 that includes a plurality ofdirectly bonded-together diamond grains bonded to a first transitionlayer 140 that includes at least one additive, diamond grains, andmetal-solvent catalyst. A second transition layer 142 is bonded to thefirst transition layer 140 and to the substrate 102, and also mayinclude at least one additive, diamond grains, and metal-solventcatalyst. During HPHT sintering, metal-solvent catalyst from thesubstrate 102 (e.g., cobalt from a cobalt-cemented tungsten carbidesubstrate) or another source sweeps into the first and secondtransition-layer mixtures 132 and 134 to cement the constituents thereoftogether. If the first transition layer 140 includes relatively morediamond grains and less of the at least one additive than that of thesecond transition layer 142, the residual stress gradient between thesubstrate 102 and the PCD layer 138 may be reduced. Other formulationsfor the transition-layer mixtures 132, 134 and the resulting transitionlayers 140, 142 may be selected to reduce the residual stress gradientbetween the substrate 102 and the PCD layer 138 and/or facilitatebonding between regions comprising differing materials. In someembodiments, at least the PCD layer 138 may be leached to at leastpartially remove the metal-solvent catalyst present in the PCD layer 138to a selected depth similar to the embodiment illustrated in FIG. 1B.

Referring now to FIG. 5, the effect on the maximum tensile stressesgenerated in the PCD layer 106 as a function of increasingtungsten-carbide content in the transition layer 104 of the PDC 100 inFIG. 1A is illustrated. Specifically, FIG. 5 illustrates finite elementmodeling results showing reduced stress in the PCD layer 106 of the PDC100 formed by an HPHT process with increasing tungsten-carbide contentin the transition layer 104 disposed between and bonded to the substrate102 and the PCD layer 106.

The finite element model models a maximum tensile stress in the PCDlayer 106 of the PDC 100 when the substrate 102 is a cobalt-cementedtungsten carbide (“WC—Co”) substrate and the PCD layer 106 andtransition layer 104 are of equal thicknesses. The transition layer 104adjacent the WC—Co substrate 102 is a mixture of diamond and WCparticles (i.e., pure WC particles). The volume percent of WC is listedon the graph. The PCD layer 106 is substantially free of WC particles.In the model, the PCD layer 106 was modeled as 100% diamond. Data wasgenerated for three different thickness of the PCD layer 106 and thetransition layer 104, which is listed on the graph (0.060-inch,0.090-inch, and 0.120-inch). The y-axis of the graph shows the maximumtensile stress in the PCD layer 106 at a simulated brazing temperatureof approximately 720° C. As can be seen from FIG. 5, the maximumbraze-temperature tensile stress (i.e., the principal stress) generatedduring brazing of the PDC 100 to another structure is significantlyreduced when the transition layer 104 includes about 25 vol % to about50 vol % WC for the at least one additive. As the maximumbraze-temperature tensile stress is significantly reduced, damage in thePCD layer 106 during brazing of the PDC 100 may be reduced oreliminated.

Finite element models of so-called standard PDCs have shown the maximumbraze-temperature tensile stress to be about 82,000 psi. Standard PDCsare fabricated, for example, in an HPHT process at a pressure of 5-6 GPaand a temperature of about 1400° C. In contrast, the high-pressurefabricated PDCs described herein are fabricated at a pressure of atleast 7.5 GPa and a temperature of at least 1000° C. High-pressurefabricated PDCs lacking a transition layer (i.e., 0 vol % WC in FIG. 5)have a braze temperature tensile stress of about 120,000 psi. StandardPDCs are generally less susceptible to brazing damage because theyexhibit lower braze-temperature tensile stresses when compared to PDCsthat are sintered at higher pressure.

As can be seen from FIG. 5, addition of the transition layer 104significantly reduces the braze-temperature tensile stress of ahigh-pressure fabricated PDC. For example, addition of a transitionlayer that contains about 25 vol % to about 50 vol % WC reduces thebraze temperature tensile stress in a PCD layer having thickness ofabout 0.09 inch to about 90,000 psi at 25 vol % WC and to about 82,000psi at 50 vol % WC. This is in the range of braze-temperature tensilestress values seen for standard-pressure PDCs.

As an alternative to or in addition to the use of at least onetransition layer for stress management in a PDC, in some embodiments,LME-type damage and braze-temperature induced damage may also be reducedin the PDCs described herein by annealing after the HPHT sinteringprocess. Referring now to FIG. 6, an embodiment of an HPHT process forfabricating a PDC is illustrated. The HPHT process includes an HPHTprocessing step followed by a high-pressure annealing step at arelatively lower temperature. In the process illustrated in FIG. 6, thecell assembly including the substrate, an optional at least one layer oftransition-layer mixture, and a layer of diamond particles are arrangedin a pressure cell. In a first step, the pressure and the temperatureare ramped up to a temperature and pressure suitable (e.g., about 1500°C. at a pressure of about 8 GPa) for forming the PDC. In the illustratedembodiment, the pressure is maintained at a maximum pressure P_(max)while the sintering temperature T_(max) is maintained for about 40seconds. In a second step, the temperature is lowered to a temperaturesuitable for annealing (e.g., about 800° C.) while holding the pressureapproximately constant at P_(max). In the illustrated embodiment, theannealing temperature T_(anneal) is maintained for about 80 seconds.Finally, the temperature is ramped down and the pressure is releasedonce the temperature has been sufficiently lowered. The times andtemperatures described for the high-pressure annealing process aremerely illustrative and other values may be employed. For example, inother embodiments, the annealing may be performed at a temperature in arange of about 650° C. to about 875° C. at a pressure of about 5 GPa toabout 10 GPa (e.g., about 5 GPa to about 7 GPa) provided thatdiamond-stable HPHT conditions are maintained.

In another embodiment for the annealing process, a PDC may be annealedat atmospheric pressure or under partial vacuum (e.g., about 10⁻⁵ torrto about 10⁻³ torr). In an embodiment, annealing may be performed at atemperature of about 650° C. to about 900° C. to about for about 5 toabout 30 minutes at atmospheric pressure or under partial vacuum.Results of such a process are illustrated in FIG. 7. FIG. 7 comparesmeasured residual compressive stress values at room temperature forunannealed and annealed PDCs with 0.070-inch thick PCD tables without atransition layer. Residual compressive stress was measured at the centerof the PCD table on the working surface. As can be seen, annealingreduces the residual compressive stress in the PCD layer.

The residual compressive stress in the PCD layer or table that isrelieved by the annealing process described in relation to FIGS. 6 and 7is a result of the mismatch between the substrate having a relativelyhigh CTE and the PCD layer having a relatively low CTE. The annealingprocess occurs at temperatures approximately the same as those used tobraze the PDCs to another structure, such as a drill bit body. Thecobalt cementing constituent of the cobalt-cemented tungsten carbidesubstrate softens (e.g., reducing of the yield stress) during theannealing process such that the body forces present in the PDC deformthe substrate near the interfacial surface between the substrate and thePCD layer or table. Consequently, the substrate exerts lessthermal-induced tensile stress on the PCD layer or table when thesubstrate expands at braze temperature as compared unannealed PDCs.

The residual compressive stresses in the PCD layer or table of the PDCso-formed may be controlled by adjusting the cooling rate from T_(max)at which sintering of the diamond particles occurs. It is currentlybelieved that the PCD layer or table exhibits relatively higher theresidual compressive stresses when the cooling rate from T_(max) isrelatively faster. In some embodiments in which higher residualcompressive stresses in the PCD layer or table are desired, theannealing step may be omitted and the PDC may be rapidly cooled fromT_(max) during the HPHT process by adjusting the electrical power (e.g.,to zero power) to the heater in the cell assembly that heats the PDCconstituents being HPHT processed.

The disclosed PDC embodiments may be used in a number of differentapplications including, but not limited to, use in a rotary drill bit(FIGS. 8A and 8B), a thrust-bearing apparatus (FIG. 9), and a radialbearing apparatus (FIG. 10). The various applications discussed aboveare merely some examples of applications in which the PDC embodimentsmay be used. Other applications are contemplated, such as employing thedisclosed PDC embodiments in wire-drawing dies and friction stir weldingtools.

FIG. 8A is an isometric view and FIG. 8B is a top elevation view of anembodiment of a rotary drill bit 900. The rotary drill bit 900 includesat least one PDC configured according to any of the previously describedPDC embodiments. The rotary drill bit 900 comprises a bit body 902 thatincludes radially and longitudinally extending blades 904 with leadingfaces 906, and a threaded pin connection 908 for connecting the bit body902 to a drilling string. The bit body 902 defines a leading endstructure for drilling into a subterranean formation by rotation about alongitudinal axis 910 and application of weight-on-bit. At least one PDCcutting element, configured according to any of the previously describedPDC embodiments (e.g., the PDC 100 shown in FIG. 1A), may be affixed tothe bit body 902. Each of a plurality of PDCs 912 is secured to theblades 904. For example, each PDC 912 may include a PCD layer and atransition layer bonded to a substrate. More generally, the PDCs 912 maycomprise any PDC disclosed herein, without limitation. In addition, ifdesired, in some embodiments, a number of the PDCs 912 may beconventional in construction. Also, circumferentially adjacent blades904 define so-called junk slots 920 therebetween, as known in the art.Additionally, the rotary drill bit 900 may include a plurality of nozzlecavities 918 for communicating drilling fluid from the interior of therotary drill bit 900 to the PDCs 912.

FIGS. 8A and 8B merely depict an embodiment of a rotary drill bit thatemploys at least one cutting element comprising a PDC fabricated andstructured in accordance with the disclosed embodiments, withoutlimitation. The rotary drill bit 900 is used to represent any number ofearth-boring tools or drilling tools, including, for example, core bits,roller-cone bits, fixed-cutter bits, eccentric bits, bicenter bits,reamers, reamer wings, or any other downhole tool including PDCs,without limitation.

The PCD and/or PDCs disclosed herein (e.g., the PDC 100 shown in FIG.1A) may also be utilized in applications other than rotary drill bits.For example, the disclosed PDC embodiments may be used in thrust-bearingassemblies, radial bearing assemblies, wire-drawing dies, artificialjoints, machining elements, and heat sinks.

FIG. 9 is an isometric cut-away view of an embodiment of athrust-bearing apparatus 1000, which may utilize any of the disclosedPDC embodiments as bearing elements. The thrust-bearing apparatus 1000includes respective thrust-bearing assemblies 1002. Each thrust-bearingassembly 1002 includes an annular support ring 1004 that may befabricated from a material, such as carbon steel, stainless steel, oranother suitable material. Each support ring 1004 includes a pluralityof recesses (not labeled) that receives a corresponding bearing element1006. Each bearing element 1006 may be mounted to a correspondingsupport ring 1004 within a corresponding recess by brazing,press-fitting, using fasteners, or another suitable mounting technique.One or more, or all of bearing elements 1006 may be configured accordingto any of the disclosed PDC embodiments. For example, each bearingelement 1006 may include a substrate 1008, a PCD layer 1010, and atleast one transition layer (not shown) disposed between the substrate1008 and the PCD layer 1010. The PCD layer 1010 includes a bearingsurface 1012.

In use, the bearing surfaces 1012 of one of the thrust-bearingassemblies 1002 bear against the opposing bearing surfaces 1012 of theother one of the bearing assemblies 1002. For example, one of thethrust-bearing assemblies 1002 may be operably coupled to a shaft torotate therewith and may be termed a “rotor.” The other one of thethrust-bearing assemblies 1002 may be held stationary and may be termeda “stator.”

FIG. 10 is an isometric cut-away view of an embodiment of a radialbearing apparatus 1100, which may utilize any of the disclosed PDCembodiments as bearing elements. The radial bearing apparatus 1100includes an inner race 1102 positioned generally within an outer race1104. The outer race 1104 includes a plurality of bearing elements 1110affixed thereto that have respective bearing surfaces 1112. The innerrace 1102 also includes a plurality of bearing elements 1106 affixedthereto that have respective bearing surfaces 1108. One or more, or allof the bearing elements 1106 and 1110 may be configured according to anyof the PDC embodiments disclosed herein. The inner race 1102 ispositioned generally within the outer race 1104 and, thus, the innerrace 1102 and outer race 1104 may be configured so that the bearingsurfaces 1108 and 1112 may at least partially contact one another andmove relative to each other as the inner race 1102 and outer race 1104rotate relative to each other during use.

The radial-bearing apparatus 1100 may be employed in a variety ofmechanical applications. For example, so-called “roller cone” rotarydrill bits may benefit from a radial-bearing apparatus disclosed herein.More specifically, the inner race 1102 may be mounted to a spindle of aroller cone and the outer race 1104 may be mounted to an inner boreformed within a cone and that such an outer race 1104 and inner race1102 may be assembled to form a radial-bearing apparatus.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments are contemplated. The various aspects andembodiments disclosed herein are for purposes of illustration and arenot intended to be limiting. Additionally, the words “including,”“having,” and variants thereof (e.g., “includes” and “has”) as usedherein, including the claims, shall be open ended and have the samemeaning as the word “comprising” and variants thereof (e.g., “comprise”and “comprises”).

1. A method for manufacturing a polycrystalline diamond compact,comprising: forming an assembly including at least one preformedtransition layer disposed between a preformed polycrystalline diamondbody and a substrate; wherein the at least one preformed transitionlayer includes a plurality of diamond grains and at least one additive;wherein the at least one preformed transition layer exhibits acoefficient of thermal expansion (“CTE”) that is less than a CTE of thesubstrate and greater than a CTE of the preformed polycrystallinediamond body; and subjecting the assembly to ahigh-temperature/high-pressure process to effective to bond thepreformed polycrystalline diamond body to the at least one preformedtransition layer.
 2. The method of claim 1 wherein the at least oneadditive includes at least one member selected from the group consistingof tungsten carbide, chromium carbide, cemented carbide, and cubic boronnitride.
 3. The method of claim 1 wherein the at least one additive isabout 25 volume % to about 50 volume % of the at least one preformedtransition layer.
 4. The method of claim 1 wherein the preformedpolycrystalline diamond body is substantially free of the at least oneadditive.
 5. The method of claim 1 wherein at least some of theplurality of diamond grains of the at least one preformed transitionlayer exhibit diamond-to-diamond bonding therebetween.
 6. The method ofclaim 1 wherein the plurality of diamond grains of the at least onepreformed transition layer exhibit substantially no diamond-to-diamondbonding therebetween.
 7. The method of claim 1 wherein the preformedpolycrystalline diamond body is at least partially leached.
 8. Themethod of claim 7 wherein, prior to being at least partially leached,the preformed polycrystalline diamond body exhibits a coercivity ofabout 115 Oersteds (“Oe”) or more and a specific magnetic saturation ofabout 15 Gauss·cm³/grams (“G·cm3/g”) or less.
 9. The method of claim 8wherein the coercivity is about 130 Oe to about 160 Oe and the specificmagnetic saturation is about 10 G·cm³/g to about 15 G·cm³/g.
 10. Themethod of claim 1, further comprising at least partially leaching thepreformed polycrystalline diamond body prior to forming the assembly.11. The method of claim 1 wherein the at least one preformed transitionlayer includes a plurality of preformed transition layers.
 12. A methodfor manufacturing a polycrystalline diamond compact, comprising: forminga polycrystalline diamond body; at least partially leaching thepolycrystalline diamond body to form an at least partially leachedpolycrystalline diamond body; separately forming at least one transitionlayer from the polycrystalline diamond body, the at least one transitionlayer formed at least partially from a mixture including a plurality ofdiamond particles and at least one additive selected from the groupconsisting of carbide particles, cemented carbide particles, and cubicboron nitride; and bonding the at least one transition layer to acarbide substrate and the at least partially leached polycrystallinediamond body to form the polycrystalline diamond compact.
 13. The methodof claim 12 wherein the polycrystalline diamond body exhibits acoercivity of about 115 Oersteds (“Oe”) or more and a specific magneticsaturation of about 15 Gauss·cm³/grams (“G·cm3/g”) or less.
 14. Themethod of claim 13 wherein the coercivity is about 130 Oe to about 160Oe, and the specific magnetic saturation is about 10 G·cm³/g to about 15G·cm³/g.
 15. The method of claim 12 wherein the at least one transitionlayer is bonded to the carbide substrate prior to bonding the at leastpartially leached polycrystalline diamond body to the at least onetransition layer.
 16. The method of claim 12 wherein the at least onetransition layer is bonded to the carbide substrate after bonding the atleast partially leached polycrystalline diamond body to the at least onetransition layer.
 17. The method of claim 12 wherein the at least oneadditive includes about 25 volume % to about 50 volume % of the mixture.18. The method of claim 12 wherein separately forming at least onetransition layer from the polycrystalline diamond body includesseparately forming the at least one transition layer in ahigh-temperature/high-pressure process.
 19. The method of claim 12,further comprising: wherein bonding the at least one transition layer toa carbide substrate and the at least partially leached polycrystallinediamond body to form the polycrystalline diamond compact includesinfiltrating the at least partially leached polycrystalline diamond bodywith a metallic infiltrant; and at least partially leaching the metallicinfiltrant from the infiltrated polycrystalline diamond body.
 20. Amethod for manufacturing a polycrystalline diamond compact, comprising:forming at least one transition layer at least partially from a mixtureincluding a plurality of diamond particles and at least one additive ina high-pressure/high-temperature process, wherein the at least oneadditive includes at least one member selected from the group consistingof carbide particles, cemented carbide particles, and cubic boronnitride; separately forming a polycrystalline diamond body from the atleast one transition layer in a high-pressure/high-temperature process;at least partially leaching the polycrystalline diamond body to form anat least partially leached polycrystalline diamond body; and bonding theat least one transition layer to a carbide substrate and the at leastpartially leached polycrystalline diamond body in ahigh-pressure/high-temperature process.
 21. The method of claim 20wherein the at least one transition layer is bonded to the carbidesubstrate prior to bonding the at least partially leachedpolycrystalline diamond body to the at least one transition layer. 22.The method of claim 20 wherein the at least one transition layer isbonded to the carbide substrate after bonding the at least partiallyleached polycrystalline diamond body to the at least one transitionlayer.
 23. The method of claim 20, further comprising: wherein bondingthe at least one transition layer to a carbide substrate and the atleast partially leached polycrystalline diamond body in ahigh-pressure/high-temperature process includes infiltrating the atleast partially leached polycrystalline diamond body with a metallicinfiltrant; and at least partially leaching the metallic infiltrant fromthe infiltrated polycrystalline diamond body.
 24. The method of claim 20wherein the at least one transition layer includes a plurality ofpreformed transition layers.
 25. A polycrystalline diamond compact,comprising: an at least partially leached polycrystalline diamond body;a cemented carbide substrate; and at least one preformed transitionlayer disposed between and bonded to the cemented carbide substrate andthe at least partially leached polycrystalline diamond body; wherein theat least one preformed transition layer includes a plurality of diamondgrains and at least one additive selected from the group consisting oftungsten carbide, chromium carbide, cemented carbide, and cubic boronnitride.